Photochemistry of the retinal chromophore in the process of seeing (vision)

• Published in: ChemTexts (Cham) Vol. 10; no. 2
• Main Authors: Das, Udita, Das, Ankita, Das, Ruhi, Das, Asim K.
• Format: Journal Article
• Language: English
• Published: Cham Springer International Publishing 08.04.2024
• Subjects: Biochemistry; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Environmental Chemistry; Lecture Text; 11; All; Vitamin A; retinal; Rhodopsin; Photoisomerization; Photopsins; Transducin; Opsin; RPE65 enzyme; G-protein coupled receptor (GPCR); Wald’s visual cycle
• ISSN: 2199-3793; 2199-3793
• DOI: 10.1007/s40828-024-00187-y

The process of vision is a complex biochemical process that involves the participation of two types of retinal photoreceptor cells: rod cells and cone cells. These visual pigments possess the chromophore, 11- cis- retinal, linked through a Schiff base linkage to the opsin protein. Absorption of light by the visual pigment leads to the photoexcitation followed by photoisomerization, 11- cis -retinal ( Z ) to all- trans -retinal ( E ) for the activation of transducin, a heterotrimeric G-protein, to generate a nerve signal that is transmitted to the brain to produce the sense of vision. The photoisomerized pigment undergoes rapid hydrolysis to produce the opsin protein and all- trans -retinal that can be reconverted enzymatically to 11- cis- retinal for recharging the opsin protein to regenerate the active visual pigment to maintain the Wald’s visual cycle. Graphical Abstract